1. Field of the Invention
This invention relates to polymers containing both imidazole and imidazolone structural units in the polymer chain and to a process for their production.
2. Description of Related Art
Polybenzimidazole polymers (hereinafter sometimes referred to as PBI polymers) are a known class of heterocyclic polymers which contain recurring units of the structure: ##STR2## where R is a tetravalent aromatic nucleus with the nitrogen atoms forming the benzimidazole rings being paired upon adjacent carbon atoms, i.e., ortho carbon atoms, of the aromatic nucleus, and R' is a member of the class consisting of an aromatic ring; an alkylene group (preferably having 4 to 8 carbon atoms); and a heterocyclic ring such as pyridine, pyrazine, furan, quinoline, thiophene, and pyran.
The following generalized equation illustrates the condensation reaction which occurs in forming the polybenzimidazoles having the recurring units as set forth above: ##STR3##
Such polybenzimidazoles are produced by the reaction of a mixture of (1) at least one aromatic tetraamine containing two groups of amine substituents, the amine substituents in each group being in an ortho position relative to each other, and (2) at least one dicarboxylic acid or derivative thereof.
Such PBI polymers are characterized by very good thermal, physical and chemical stability and may be formed into fibers, films and membranes. Examples of such PBI polymers, their process for production and articles prepared therefrom are disclosed in U.S. Pat. Nos. 3,987,015, 4,312,976, 4,431,796, and 4,814,530, the complete disclosures of which references are incorporated herein by reference.
PBI polymers which have been modified to enhance their properties of thermal stability and solvent solubility are also known in the art. For example, U.S. Pat. No. 3,671,491 discloses the preparation of random benzimidazole-benzoxazole copolymers prepared by condensing a mixture of an aromatic tetraamine (such as 3,3'-diamino benzidene), a hydroxy substituted aromatic diamine (such as 3,3'-diamino4,4'dihydroxy biphenyl) and an aromatic dicarboxylic acid or derivative thereof (such as diphenyl isophthalate).
Another category of polymer material exhibiting high thermal stability are the polybenzimidazolone polymers (hereinafter sometimes referred to as PBIL polymers). Such polymers may be generally characterized as containing recurring units of the structure: ##STR4## wherein Ar and Ar.sub.1 are the same or different aromatic nuclei. Precursors of these PBIL polymers are generally prepared by forming the condensation reaction product of an aromatic tetraacid or derivative, or an aromatic dianhydride (such as biphenyl dianhydride) and an aromatic tetraamine (such as 3,3'-diamino benzidene). Such polymers are disclosed in Marvel, C.S. Journal of Polymer Science, Part A, (3), p. 3549, (1965).
Similar PBIL polymers are also disclosed in U.S. Pat. No. 3,987,015 which teaches a process for the preparation of both PBI and PBIL polymers in finally divided particulate form.
U.S. Pat. No. 4,260,652 discloses a process for producing a permselective composite membrane wherein a significant number of what are referred to as polybenzimidazolone polymers are disclosed. See for example, columns 33 through 44. The polybenzimidazolone polymers disclosed may or may not include polyphenyl rings linked by bridging members selected from the group consisting of: --O, --SO.sub.2 --, --CO, --CH.sub.2 --, and --C(CH.sub.3).sub.2 --.
U.S. Pat. No. 4,656,244 discloses a process for the preparation of radiation-reactive precursors of PBI and PBIL polymers wherein an aromatic or heterocyclic tetraamino compound (such as diaminobenzidene) is reacted with an olefinically unsaturated monocarboxylic acid (such as acrylic acid) and an aromatic dicarboxylic acid (such as isophthalic acid) to produce modified PBI type polymers, or with an aromatic tetraacid or derivative thereof (such as pyromellitic dianhydride) to produce PBIL type polymers. These precursor polymers are said to exhibit photosensitivity due to the presence of the added olefinically unsaturated compound in the precursor polymer molecules. A wide variety of aromatic structures and groups linking these aromatic structures are disclosed on columns 4-9 of this patent.
Copending application Ser. Nos. 07/494,009, filed in the USPTO on Mar. 15, 1990, and 07/505,742 filed in the USPTO on Apr. 6, 1990 disclose PBIL type polymers prepared by forming the polymer condensation product of an organic tetraamine such as 3,3',4,4'-tetraamino biphenyl or 2,2,-bis (3,4-diaminophenyl) hexafluoropropane and an aromatic dianhydride containing a hexafluoroisopropylidene group such as 2,2'bis(3,4-dicarboxy phenyl) hexafluoropropane dianhydride.
Copending application Ser. No. 07/487,330, filed in the USPTO on Mar. 1, 1990, discloses PBI type polymers prepared by forming the polymer condensation product of 2,2'-bis(3,4-diaminophenyl) hexafluoropropane with an aromatic dicarboxylic acid such as isophthalic acid or 4,4'-diphenyl-hexafluoroisopropylidene dicarboxylic acid.
The polymers of these copending applications are characterized as having improved solvent solubility, low temperature processibility, low moisture absorption, high thermal stability, resistance to solvents after curing, excellent mechanical properties, easy blending with other polymers, low dielectric constants, and excellent electric properties when compared to PBI and PBIL polymers which do not contain the fluorine-containing linking groups.